Alternative control system for fluid-operated motors



1952 B. E. TREGANOWAN 2,618,243

ALTERNATIVE CONTROL SYSTEM FOR FLUID-OPERATED MOTORS Filed Aug. 2, 1948 2 SHEETS-SHEET 1 18, 1952 B. E. TREGANOWAN 2,613,243

ALTERNATIVE CONTROL SYSTEM FOR FLUID-OPERATED MOTORS Filed Aug. 2, 194a 2-SHEETS-SHEET 2 Patented Nov. 18, 1952 UNITED SE'A'E'ES OFFICE ALTERNATIVE CONTROL SYSTEM FOR' FLUID-OPERATED MOTORS Application August 2, 1948, Serial No. 42,082 In Great Britain August 20, 1947 9 Claims.

This invention relates to fluid pressure, partlcularly pneumatic pressure operated control systems, more particularly for use in aircraft.

It is common practice in hydraulic or pneumatic distant control systems provided to operate undercarriages, flaps, bomb doors and like apparatus on an aircraft, to provide a normal transmission line for carrying pressure fluid for normal operations and separately from this an emergency line which is capable of being operated when the normal transmission line is thrown out of action. In aircraft where the normal operation is effected by hydraulic or pneumatic means, the emergency operation generally comprises an accumulator storing gas under pressure with a supply line leading to the operating means, for example a jack.

The various arrangements embodying this construction which have hitherto been proposed are, however, subject to certain objections especially as regards the lowering of undercarriages in case of an emergency. When a double acting jack is used to operate an undercarriage, the pressure applied to one side of the piston has to force the fluid from the other side to the tank or exhaust, thus dissipating energy. This in practice will act as a sort of cushion on the action of the piston. If, on the other hand, the normal operation means have failed, the pressure in the jack cylinder is liable generally to be down to atmospheric pressure. If the pressure in the emergency line is then applied to the jack piston no resistance will be offered to its movement. so that the action of the jack may become too violent so that the piston is liable to damage due to impact or to be shorn off the piston rod.

One object of this invention is to provide an alternative operating system which when used in aircraft becomes an emergency operating system, that is to say an operating system which is brought into action when the normal operating system fails, and in which the above disadvantage'is minimised.

According to onefeature of the invention a pressure-operated control system comprises a supply of pressure fluid, a fluid motor such as a jack, means for'placing the supply of pressure :fluid in communication'with both sides of the jack piston, the supply :to one side of the differential piston beingunrestricted, while the supply to the other :side of the jack piston is restricted, and control means operable. firstly by pressure in the unrestricted line to allow-pressure to be built up in one side. of; the jack cylinder and subsequently by pressure 'in the restricted line automatically to cut oil supply of pressure 'fiuldxto the jack cylinder through the unrestrictedline without interfering with supply of pressure 'fluid to the other side of, the jack cylinder through therestricted line to operate the jack.

According to another feature of the invention the system comprises an alternative supply of pressure fluid capable of being placed in communication with both sides of the normal jack piston by an alternative operation valve, the alternative pressure fluid supply line to one side of the jack piston being unrestricted whilst the alternative pressure fluid supply line to the other side of the jack piston is restricted.

Control means may be provided which means are operable firstly by pressure in the unrestricted line to allow pressure to be built up in one side of the jack cylinder and subsequently by pressure in the restricted line to out ofi supply of pressure fluid to the jack cylinder through the unrestricted line and allow supply of pressure fluid to the other side of the jack cylinder through the restricted line to operate the jack. Such control means preferably comprises a shuttle control valve in communication with the alternative unrestricted supply line at one end and at the other end with the restricted line and in communication also with one side of the jack cylinder.

Two forms of the invention as applied to undercarriage equipment are diagrammatically illustrated in the accompanying drawings. Figure '1 shows the invention applied to a pressure operated system in which only a small efiort is needed to lower the undercarriage, that is to say one in which the emergency "pressure acting on both sides of the jack piston as a differential jack pis ton is suflicient to lower the undercarriage. Figures 2 and 3 illustrate a more complicated form of system applied to a pneumatically operated control system for aircraft parts and in which it is necessary to apply a higher emergency pressure to one side of the jack piston in order to efiect operation, for example the lowering of the undercarriage.

Referring to the arrangement shown in Figure 1, the normal control system includes the usual compressor or compressors with accessories producing'pressure for normal operation, and any known locking means incorporated in the undercarriage and/or in the jack to maintain the undercarriage retracted when the normal Op l..- atingsystem .fails. None of these parts, however, are shown in the figure.

If the system is ;-.pneumatically operated :the

gas, preferably air, "is stored .in an -.accumu1a. tor l having a connection 2 to, for example, an undercarriage selector 3. The said selector has two connections with the undercarriage operating jack, one line 4 leading to one side of the piston I to cause retraction of the undercarriage, and the other line 5 to the other side of the piston I to cause extension of the undercarriage, the selector being provided with an exhaust outlet 6. The jack 'II is of the double acting type and serves for the normal and emergency operation of the system, while the jack piston is a motorv piston of the differential type, that is to say one eflective area of the piston is larger than the other. In order to separate the normal system from the emergency system, the supply lines from the selector are led to the jack via two shuttle valves 8, 9.

The emergency system comprises an emergency accumulator ID the supply of pressure fluid from which is controlled by an emergency operation valve II which connects the accumulator to a supplyline l2 leading to the jack piston. This supply line is branched to provide an unrestricted supply line l3 to one side of the piston, whilst the other branch is restricted by a restrictor I4, thus providing a restricted supply line 15 to the other side of the jack cylinder, both the unrestricted and restricted supply lines communicating with the jack cylinder respectively through the shuttle valves 8, 9. The emergency operation valve H which is shown diagrammatically in the drawings is merely an alternately operable supply and exhaust valve of common, well known type. The chamber 33 is in communication with the accumulator I and contains air under pressure. The chamber 3% is in communication with the jack through the lines l2, I3 and I4. Extending through the chamber 34 is a valve stem 35 which carries an inlet valve 31 and an exhaust valve 38. The stem 35 may be moved by a handle or actuator 36 to cause closing of exhaust valve 38 and opening of valve 31, thus permitting pressure fluid to flow into line I2. Upon movement of the handle 36 in the other direction, inlet valve 3! closes,

interrupting pressure fluid flow to the jack, and exhaust valve 38 may open, allowing the pressure fluidxin' chamber34 and the supply lines i2, I3

and I4 to pass out to the atmosphere.

During the normal operation of the system to obtain retraction of the jack piston, pressure fluid supply from a compressor passes from the undercarriage selector 3 through the supply line 4 and actuates the shuttle valve 8 so that pressure fluid is admitted to the underside of the piston -'I inthe jack cylinder, pressure fluid from the other side being exhausted through line 5 and exhaust 6; for extension of the jack piston, pressure fluid is admitted through line 5 and exhausted through line 4.

Should the normal operating system due to any causebe placed out of action, the resulting leak may ultimately lead to a drop of pressure in the said supply lines down to atmospheric pres- .sure and in order to operate the jack it becomes necessary to operate the emergency supply system. In the case of it being desired to lowerthe undercarriage under emergency conditions, the emergency valve II is operated allowing the air stored under pressure in the emergency accumulator, I0 to pass into the supply line l2. The

pressure fluid will pass through the branch of sure in the unrestricted line I3 to increase more rapidly than in the restricted line l5; thus the air under pressure in the unrestricted line I3 flows into the shuttle valve 8, thereby causing movement of its piston 8| so as to place the unrestricted line I3 into communication with one side of the jack cylinder, that is to say the side which normally is used for retraction of the jack piston. The pressure fluid passing through this shuttle valve 8 moves its piston 8| so as to isolate the connection between the shuttle valve and the jack cylinder from the normal working system; thus pressure is built up on the retraction side of the piston 'I in the jack. Air under pressure also passes through the line l5, in which the pressure builds up at a slower rate as a result of the restrictor l4, and through the shuttle valve 9 at the other side of the jack moving its piston 9| so as to allow pressure fluid to enter the jack cylinder II on the other side of the piston l, causing therefore the jack piston I to move so as to lower the undercarriage, rapid movement of the piston being prevented due to the pressure being built up on the other side thereof.

It will be appreciated that when air under pressure is entering the emergency pipe lines from the accumulator I 0, the restrictor M will not maintain the pressure on the full area of the piston I permanently lower, but only temporarily over a very short space of time, and as soon as the pressure on the full piston area is nearing the pressure of that on the underside of the piston I, the jack II will extend and the air from: the underside of the piston I will return into the emergency system which is a closed system with a substantially predetermined pressure; thus the pressure tends to equalise itself in this closed system, and the restrictor will only retard temporarily this tendency to supply pressure for one branch, thus producing the cuhioning eiTect.

Referring now to the system shown in Figures 2 and 3 the normal operating system is the same and the jack II functions as a double acting jack serving for the normal and emergency operation of the system, the jack piston being either of the differential type or having two piston rods of equal diameters extending through the end walls of the cylinder. In the emergency circuit, however, there is provided the accumulator I0 and emergency control valve II which connects the accumulator to the supply line I2 branched to provide the unrestricted line I3 and the line I5 restricted by the restrictor I4. The line I3 is connected to one end of a shuttle control valve I6 and the line I5 is also branched as at I! to communicate with the opposite end of the shuttle control valve I 6. This valve is provided with two outlets, one I8 to exhaust and the other I 9'to the jack H. As in the previous arrangement the unrestricted and restricted supply lines I3, l5 communicate with the jack 'II respectively through the shuttle valves 8, 9.

The shuttle control valve IB comprises a cylinder in which slides a piston rod 20, two pistons 2|, 22, one at each end of the piston rodoand two valve seats 23, 24 which allow one of the pistons to seat alternatively thereon.

During normal operation of the system, for retraction or extension of the jack piston, pressure fluid supplied through the supply lines 4 or 5, from the undercarriage selector 3, moves the shuttle valves 8 or 9, so that pressure fluid is admitted to one or the other side of the piston I in the jack cylinder II Should the normal operating system, due to any cause, be placed out pfaaction-rth'e. resultingBleak may ultimately lead 1207a;drop!oipressureinthe said supplylines down toicatmosphericipressure; and in :order to operate 'Ithe ijackiritflbecomes necessary to operate *Jthe aemergencyfisupplysystem. In .the case of it being 'desir'editotlower, und'ercemergency conditionathe undercarriage, "ithe emergencyvalve ll'is operatedvallowingaair stored under pressure in the accimmlator; 'to pass through :into the supply Jline 132-... a'I'hezpressurefluid will passathrough'the' branch of theunrestricted line [.3 into the shuttle control valve l6, while the pressure fluid :also passes-through the'zrestrictor '14 into the. restrictedfsupply line ll5,"bl1t as a result. of the action :of the zrestrictor. the. pressure 'in' the unrestrictedzline l3'will increase morerapidly than in therestricted line 15:; *thusth'eair :iunder pressure 'lnz the unrestricted :.;lin'e. :I 3. :flows' :into the shuttlecontrol valve 15 thereby causingrmovement'pf'lthezpiston.22-so..as to place". the shuttle rcontrol valve .into communication with the *shuttlevalve 8,-that is to saytheva'lve which is normally usedfor retractionof the jack piston. The pressure fluid passing *throughthis valve 8 moves its piston-8i so as to isolate theconnec- -tion :between "the'valve 8 and jack 1! from the normalwork-ing system, sothat-pressure is built up on :the retraction side-of the piston 1 in the jack. Air under pressure also passesthrough the line --l5,in which'pressu-re is built up at a slower rate .as a result'of the actionof the restrictor It through the shuttle valve 9 moving itspiston-B soas-to allow pressurefluid to enter the cylinde H at :the other side of the piston l causing,

therefore, the jack piston 7 to move so as to lower the undercarriage, rapid movement of the .piston being prevented due to the pressure being built up on the other side thereof. At the same time pressure fluid in the restricted line l passes through its branch I! into the other end of the shuttle control valve cylinder l6 so as to move the piston 2|, piston rod 28 and piston 22 back again in reverse direction cutting off the supply of pressure fluid to the jack through the urn restricted -line I3 and allowing the shuttle control valve to open to exhaust at I8. Due to the provision .of the restrictor [4 this return movementof the shuttle control valve 16 will only take place after suflicient pressure has been built upon the retraction side of the piston in the jack H so that substantially the full pressure of the emergency accumulator l0 can act on the jack piston 1 to lower the undercarriage. The pressure fluid on the other side of the jack piston I is forced through the shuttle valve 8 into the shuttle control valve l6 and from there to exhaust l8. Figure 3 shows the parts of the shuttle control valve l6 and shuttle valves 8 and 9 in their operative position when pressure fluid is fed from the accumulator l0 through the lines l3 and [5. As the pressure fluid from the retraction side of the jack piston is being exhausted through exhaust outlet I8 of the valve l6 after a'predetermined pressure has been reached, a system incorporating the valve device I6 can be operated even if the jack piston has an equal area on both sides exposed to pressure so that the jack piston is non-difierential.

As shown in Figures 2 and 3, the piston. 22 may be biassed by a spring 22a, its diameter being smaller than the diameter of the other piston 2 i or any other known means to assist return may be provided.

Although the particular embodiment of the invention described above with reference to the drawings is so described as :appliedito emergency operation, it :is'to be understood thatth'e invention is "also applicable in certain cases 'to. normal operation of the jack'in'which case-on operation of the jack, pressure :fluidis admitted to both sides of .the jack .zpiston, there being provided controlmeanszoperable firstly by pressure in the unrestricted line to :allow pressure to be built up in one-side of the jack cylinder, and subse- "quently by pressure in the restricted line automatically' to out 01f supply of pressure fluid to the jack cylinder through the unrestricted line, and? allow supply of pressure fluid to the other side of the *jack cylinder through the restricted line to operate the jack piston, whereby the fluid from the rfirst side-ofv thejackpistonis exhausted.

What I claim .is

1; 1A pressure-operated control system zoom prising a supply :of'jpressure fluid, a "fluidmotor including a cylinder .and adifferential piston therein, means :for placing the supply of pres- *sure fluid in communication with said cylinder on both sides of said. pistoniincludin'g a :supply line to the cylinder on one side of the piston which 'is unrestricted and a supply line to the cylinder on the other side of the piston which is restricted, and control means operable flrstly by pressure in the unrestricted line to allow pressure to be built up in the cylinder on one side of the piston and subsequently operable by pressure in the restricted line automatically to cut off supply of pressure fluid through the unrestricted line to said cylinder on said one side of said piston and thereafter to establish communication between said cylinder on said one side of said piston and the atmosphere, thereby permitting exhaust of pressure fluid therein.

2. In a pressure-operated control system, a normal supply of pressure fluid, an alternative supply of pressure fluid, a fluid motor including a cylinder and a diflerentia] piston therein, means for placing the alternative supply of pressure fluid in communication with said cylinder .on both sides of the piston, said means comprising an alternative operation valve, an unrestricted alternative pressure fluid supply line to the cylinder on one side of the piston, a restricted alternative pressure fluid supply line to the cylin- -der' on the other side of the piston, and control means operable flrstly by pressure in the unrestricted line to allow pressure to be built up in the cylinder on one side of the piston, and subsequently operable by pressure in the restricted line automatically to cut off supply of pressure fluid through the unrestricted line to said cylinder on said one side of said piston and thereafter to establish communication between said cylinder on said one side of said piston and the atmosphere, thereby permitting exhaust of pressure fluid therein, and valve means in each of said supply lines operable by pressure therein to prevent flow of pressure fluid from said normal supply to said cylinder.

3. A system as claimed in claim 2 in which the control means comprises a shuttle control valve mechanism in communication at one of its ends with the alternative unrestricted supply line and at the other one of its ends being in communication with the restricted supply line and in communication also with one side of said cylinder.

4. A system as claimed in claim 2 in which said valve means comprises a shuttle valve in said unrestricted supply line and a shuttle valve in said restricted supply line.

5. A system as claimed in claim 4 in which the said control means comprises a shuttle control valve in communication at one of its ends With the unrestricted supply line and in communication at the other of its ends with the restricted supply line and also with said cylinder;

6. A pressure-operated control system comprising a normal supply of pressure fluid, a fluid motor comprising'a cylinder and a differential piston therein, and means for controllably supplying fluid under pressure to said motor'for operating said piston including an alternative supp y of pressure fluid, an operation valve for placing said alternative supply of pressure fluid in communication with both sides of said piston, a restrictedalternative pressure fluid supply line leading from said operation valve to said cylinder on one side of said piston, an unrestricted alternative pressure fluid supply line leading from said operation valve to said cylinder on the other side of the piston, and valve means in each of said supply lines operable by pressure therein to prevent flow of pressure fluid from said normal supply to said cylinder. 1 '7. A system as claimed in claim 6 in which said valve means comprises a shuttle valve interposed in said restricted supply line, and another shuttle valve interposed in said unrestricted supply line.

8. In a pressure-operated control system, a fluid motor including a cylinder and a differential piston, a normal supply of pressure fluid, a first supply line adapted to communicate with said cylinder on one side of said piston, a second supply line adapted to communicate With said cylinder on the other side of said piston, an exhaust, a selector valve mechanism for selectively placing one of said supply lines in communication with said normal supply and the other of said sup-ply lines in communication with said exhaust, and vice versa, an auxiliary supply of pressure fluid, a third and relatively unrestricted pipe line adapted to communicate with said cylinder on saidone side of said piston, a fourth and relatively restricted pipe line adapted to communicate with said cylinder on said other side of said piston, means for placing said third and fourth pipe lines jointly in communication with said auxiliary supply, and valve means responsive to pressure in said first or second pipe lines and the relative absence of pressure in said third and fourth pipe lines for establishing communication between said cylinder and said first or second pipe lines, according to which of said first and second pipe lines is pressurized, and responsive to pressure in said third and fourth pipe lines and the relative absence of pressure in said first and second pipe lines for establishing communication between said third and fourth pipe lines and said cylinder'respectively on opposite sides of said piston.

9. In a pressure-operated control system, a normal supply of pressure fluid, an alternative supply of pressure fluid, a fluid motor including a cylinder and a piston therein, means for placing the alternative supplyof'pressure fluid in communication with said cylinder on both sides of the piston, said means comprising an alternative operation valve, an unrestricted alternative pressure fluid supply line to the cylinder on one side of the piston, a restricted alternative pressure fluid supply line to the cylinder on the other side of the piston, control means operable firstly by pressure in the unrestricted line to allow pressure to be built up in the cylinder on cneside of the piston, and subsequently operable by pressure in the restricted line automatically to cut oil supply of pressure fluid through the unrestricted line to said cylinder on said one side of said piston andthereafter to establish communication between said cylinder on said one side of said piston and the atmosphere, thereby permitting exhaust of pressure fluid therein, and valve means in each of said supply lines operable by pressure therein to prevent flow of pressure fluid from said normal supply to said cylinder.

BERNARD ERIC 'I'REGANOWAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 7 1,156,855 Akans Oct. 12, 1915 2,186,235 Brown Jan. 9, 1940 2,381,923 Obtresal Aug. 14, 1945 

